The following one has been proposed as a transparent member to be used for a showcase for commercial products, etc., a display case for works of art, etc., a window of a building, showroom, vehicle, etc., a glass door, an indoor transparent partition, etc.
An image display transparent member (so called a transparent screen), through which a scene on the opposite side of the transparent member as viewed from an observer's side can be seen, and which displays image-forming light projected from a projector so as to be visible as a screen image to the observer, at the time of transmitting information such as description of commercial products, etc., states of various kinds of equipment, destination guides, messages, etc., to the observer, at the time of displaying operation scenes of various kinds of equipment to the observer, or at the time of making a scene on the opposite side of the transparent member to be not seen through to the observer for the sake of privacy protection, security, etc.
As transparent screens, there are a reflection-type transparent screen which displays image-forming light projected from a projector so as to be visible as a screen image to an observer who is on the same side as the projector; and a transmission-type transparent screen which displays image-forming light projected from a projector so as to be visible as a screen image to an observer who is on the opposite side of the projector.
As a transmission-type transparent screen, for example, as shown in FIG. 17, a transmission-type transparent screen 101 has been proposed which has a light-scattering layer 134 comprising a transparent resin 132 and a light-scattering material 133 (e.g. hollow beads), between a first transparent substrate 110 and a second transparent substrate 120 (see Patent Document 1).
In the transmission-type transparent screen 101, image-forming light L projected from a projector 200 and entered from the surface (first surface A) on the first transparent substrate 110 side, is scattered in the light scattering layer 134 to form an image and displayed so as to be visible as a screen image to an observer X who is on the opposite side of the projector 200.
Further, in the transmission-type transparent screen 101, light of a scene on the first surface A side enters into the transmission-type transparent screen 101 from the first surface A, whereupon a part is scattered in the light scattering layer 134 and the rest is transmitted. Thus, if no image-forming light L is projected on the transmission-type transparent screen 101 from the projector 200, the observer X on the second surface B side can see through the scene of the first surface A side. Likewise, light of a scene on the second surface B side enters into the transmission-type transparent screen 101 from the second surface B, whereupon a part is scattered in the light scattering layer 134 and the rest is transmitted. Thus, if no image-forming light L is projected on the transmission-type transparent screen 101 from the projector 200, an observer on the first surface A side can see through the scene of the second surface B side.
However, in the transmission-type transparent screen 101, as shown in FIG. 18, light L1 of a scene on the first surface A side, light L2 emitted from an illumination 202 (or the sun) on the second surface B side, etc. are scattered in the light scattering layer 134, whereby the entire transmission-type transparent screen 101 may look cloudy. Therefore, even in a state where no image-forming light L is projected on the transmission-type transparent screen 101 from the projector 200, there is a problem such that for the observer X, it is difficult to see through the scene of the other side of the transmission-type transparent screen 101.
Further, even in a state where image-forming light L is projected from the projector 200 to the transmission-type transparent screen 101, unnecessary scattering of light occurs in the light scattering layer 134, whereby there is a problem such that the contrast of the image is lowered, and it is difficult for the observer X to visually recognize the screen image.